Now here's something I thought was broadly known out there: NEVER BUY OR SELL (RELATIVELY) IMMEDIATELY AFTER AN EVENT TOOK PLACE. If people are that nervous (or is it stupid), they don't have any business doing what they do - don't take my word for it, simply ask the renowned traders.
Furthermore, your argument doesn't take into account that some 20 years ago (May 2000), Sterling was much weaker to the tone of over 43% (mind you, weaker without any signs of the UK leaving the EU).
But hey it's a free world, I suggest that you just go on believing in what you choose to.